In Rising, the life signs detectors were clearly able to differentiate between humans (blue) and Wraith (red). In later episodes, they did not have this ability. It may just be that the user can select certain signs on the screen and change their color to red for usability purposes or the ability may have been considered too powerful and a deus ex machina so it was changed.

It is also possible to upload maps to the detector, so walls and other built structures would be shown additional to the life signs. This was once used to upload a Hive-Ship map, but due to changes to the ships structure this was not useful. (SGA: "Infection") The device also appears to have a map of Atlantis in its memory. (SGA: "The Storm", "The Eye")

The on-screen prop appears to be an HP IPAQ 5555 in a special acrylic case.